1. Field of the Invention
This invention relates to an improved high performance honeycomb made from a paper containing poly(paraphenylene terephthalamide) fiber and aliphatic polyamide binder and articles made from the honeycomb.
2. Description of Related Art
U.S. Pat. No. 5,137,768 to Lin; U.S. Pat. No. 5,789,059 to Nomoto; and U.S. Pat. No. 6,544,622 to Nomoto disclose honeycombs made from sheets of high modulus para-aramid materials. These honeycombs are highly prized for structural applications due to their high stiffness and high strength-to-weight ratio. Generally these honeycombs are made from papers comprising para-aramid floc, pulp, and/or other fibrous materials plus a binder. The modulus of the final honeycomb is directly related to the proportion of para-aramid fiber in the paper composition. At the same time, the proportion of para-aramid fiber in the paper is limited to a certain degree because a binder must also be present to provide the paper with adequate strength to process the paper into honeycomb. Specifically, it is believed that adhesion of the binder to the fiber in the paper is critically important in manufacture of superior honeycomb. If the selected binder for the paper does not adhere well with the fiber, the resulting paper will not have adequate strength to survive the manufacture of the honeycomb, or the resulting honeycomb will not function as a unified structure. Simply increasing the quantity of a poor binder in the paper will not adequately compensate for this lack of adhesion.
What is needed therefore is a binder that has superior adhesion to the fiber and provides a paper having adequate strength for processing. Such a binder also provides more flexibility in designing a honeycomb in that it can provide a route to minimize the total amount of binder in the paper composition and therefore increase the amount of para-aramid fiber in the paper composition and honeycomb; or if excess binder is used, reduces or eliminates the need for a thermoset matrix resin in the honeycomb.